Calcium channel inhibitors (CCI's) and calcium channel activators (CCA's) are thought to affect calcium flux through membrane bound channels as their major site of action. There are reports of clinical trials involving over 150 patients suggesting that CCI's also have beneficial effects in neuropsychiatric disorders. There are four major subclasses of CCI's, and each appears to have different biochemical and behavioral properties. Additional studies have suggested a complex interaction between dopamine receptor function and calcium channels. We are currently investigating verapamil and nifedipine as treatments for schizophrenia and tardive dyskinesia. Patients on these protocols are tested with regional cerebral blood flow and computer analyzed brain electrical activity mapping. The platelets of these patients are also studied for 3H-nitrenidipine and 3H-yohimbine binding, as well as for differential patterns of protein phosphorylation.